594 Saturated and Superheated Steam.
the volume of i Ib. weight is 26*36 cubic ft, termed *
volume : and the latter always = relative volume x 016*
Def. i. The Saturation Point is attained iv*'
latent heat required for the steam has been f " '
Def. 2. The Boiling Point occurs when the tetf *
water overcomes the surrounding pressure.
Def. 3. Dry Saturated Stearn is that which k<* *
volume, pressure, and temperature, correspMt* * ;
Def. 4, Wet Saturated Steam is in process </. ^
and is in contact with the water.
Def. 5. Superheated Steam is that which h** '
perature raised above formation point.
Def. 6. Specific Volume is the number of cttbi*
Ib. weight, and SPECIFIC DENSITY is the nuws?"
in a cubic ft. (See pp. 766^^933.)
Dryness Fraction. If the weight of water pat*11
given volume of wet steam be measured by suitable ^
the proportionate wetness will be shewn when that **-*
divided by the total weight of dry steam and water 4
while the proportionate dryness, or
TA r . weight of dry steam (See Appen* f
Dryness fraction - -- ^
f : thermometer,
Curves of Saturation Points. The cont| «,!**"*'
temperature and pressure of dry saturated steam I * *
proved by experiment From - 22° to 32°, Gay-Lus»»f **«/**
apparatus in Fig. 604* Both barometer tubes have vat * *
the mercury, but B has a, little water on the surface of the*
whose vapour pressure reduces the height of the
i in. of mercury represents about £ Ib. per sq. in., the -w
therefore known. Various freezing mixtures successivelf* * «^v,i
the blind end of tube 3, their temperature being
Fig. 605 was Regnaulfs apparatus for temperature*
to 122*. As before, barometer A bus* a perfect
B*S vacuum is impaired by vapour,, rising from water 4